Novel solid acid catalyst

ABSTRACT

A solid acid catalyst represented by HTi x Nb y O 5  wherein x is 1.1&lt;x&lt;1.2 and y is 0.9&gt;y&gt;0.8, having a Ti/Nb atomic ratio z of 1&lt;z&lt;1.5, and has been produced by subjecting a cation exchangable lamellar metal oxide composed of polyanion nano-sheets comprising lamellar metal oxide layers of titanium niobate being arranged regularly while sandwiching an alkali metal cation between them to the proton exchange of the alkali metal cation by the use of an inorganic acid or an organic acid prepared into a 0.0001M to 1M solution, and then inserting a cation selected from the group consisting of an organic amine and an organic ammonium between the resulting proton exchanged layers, to thereby delaminate the laminated layers temporarily and prepare an aqueous colloidal solution comprising metal oxide sheets having the organic amine or organic ammonium adsorbed thereon, and then adding an inorganic acid or an organic acid prepared into a 0.0001M to 1M solution to the colloidal solution, to thereby exchange the organic amine or organic ammonium with a proton and simultaneously coagulate the resulting products onto the titanium niobate nano-sheet.

FIELD OF THE INVENTION

The present invention relates to a novel solid acid catalyst obtained byusing anion nano-sheet comprising lamellar metal oxide layers oftitanium niobate containing alkali metal ion as a starting material,changing said sheet to a proton exchanger, cation exchanging said protonexchanger with organic amine or organic ammonium, removing said layersso as to prepare a colloidal solution, then re-coagulating and protonexchanging said colloidal solution by prepared protonic acid, wherein aTi/Nb atomic ratio z is in the range of 1.1<z<1.5.

DESCRIPTION OF THE PRIOR ART

Realization of chemical synthesis truly harmonized with environment is afundamental theme for constructing a scientific technique of 21^(st)century reconsidering the problems of energy and environment. Mainly,organic reactions which combine carbon with carbon are progressed byLewis acid catalyst. Among said circumstances, designing andconstruction of an acid catalyst which proceeds specifically a peculiarreaction in water, which is safe solvent, maintaining an activity of thecatalyst is an unavoidable factor for the realization of said theme.Considering said theme, many researchers are concerning with researchand development of various Lewis acid catalysts, Br ø nsted acidcatalysts or composite catalysts thereby and earnestly trying to developa high activated “super acid catalyst”. By these developments, catalyticreactions such as ester dehydration condensation or amide dehydrationcondensation, which were impossible by conventional arts, are realized.

Among these developments, solid acid catalysts such as zeolite orperfluorosulfonic acid resin are paid attention from the views, pointthat the recovery from a reaction system and reuse are easy, and a“super acid catalyst” characterizing by loadingpentafluorophenylbis(trifuril)methane (C₆F₅CHTf₂) to polystyrene resinis proposed as a solid catalyst which progresses organic reactioneffectively (Ishihara, K; Hasegawa, A; Yamamoto, H. Angew. Chem. Int.Ed. 2001, 40, 4077., Document 1).

On the contrary, the inventors of the present invention have continuedthe investigation to prepare a solid acid catalyst from polyanionnano-sheet. In “AbstractI” of the 81^(st) annual forum of Japan ChemicalSociety (2002) issued on Mar. 1, 2002, page 165 (3C5-31) (Document 2), atrial of designing of a solid acid catalyst which uses polyanionnano-sheet and the structure of which is controlled in nano level byconstructing a self-organized macro molecule and by which liquid phaseesterfication reaction can be specifically controlled is tried. However,in this trial, only a solid acid catalyst obtained by removing,re-coagulating lamellar metal oxide of Ti/Nb=1 and Ti/Nb=2 is proposed,and in the trial, the element ratio of Ti/Nb and activity of solid acidcatalyst, especially the activity in liquid phase esterfication reactionare not referred at all. Further, in “Abstract of Session A” of the90^(th) Catalyst Forum of Catalyst Society issued on Sep. 10, 2002, page183 (4E09) (Document 3), the element ratio of Ti/Nb and activity ofsolid acid catalyst are referred, and in said document, it is reportedthat the catalyst is more activated at Ti/Nb=0.818, which is smallervalue than 1.

The subject of the present invention is to provide a high effectivesolid acid catalyst which is active than the proposed solid acidcatalyst mentioned above using a polyanion nano-sheet having alkalimetal cation between layers, in particular, using a lamellar metal oxidecontaining titanium, niobium and alkali metal. For dissolving saidsubject, the inventors of the present invention have carried out variousexperiments by trial and error as follows. That is, a lamellar metaloxide containing titanium, niobium and alkali metal in which blendingratio of titanium a niobium is changed is synthesized, then theresulting lamellar metal oxide is cation exchanged with organic amine ororganic ammonium and layers are re-laminated. Two dimensionalre-coagulated sheet is prepared by adding acid and a liquidesterfication reaction is tried using said two dimensional re-coagulatedsheet, and it is confirmed that very activated solid acid catalyst canbe obtained at Ti/Nb ratio z is 1<z<1.5, especially at z is 1.2<z<1.4,thus the subject of the present invention is dissolved.

SUMMARY OF THE INVENTION

The first one of the present invention is, (1) a solid acid catalystrepresented by HTi_(x)Nb_(y)O₅, wherein x is 1.1<x<1.2 and y is0.9>y>0.8, having a Ti/Nb atomic ratio z of 1<z<1.5, obtained by protonchanging of alkali metal cation of cation changeable lamellar metaloxide in which polyanion nano-sheet comprising lamellar metal oxidelayers of titanium niobate lying alkali metal cation between areregularly laminated by inorganic acid or organic acid adjusted to0.0001M to 1M, delaminating said laminated layers temporarily byinserting cation selected from the group consisting of organic amine ororganic ammonium between layers of proton exchangers, preparing anaqueous colloidal solution comprising metal oxide sheets to which saidorganic amine or organic ammonium is absorbed, then proton exchangingsaid organic amine or organic ammonium by adding inorganic acid ororganic acid adjusted to 0.0001M to 1M to said aqueous colloidalsolution and simultaneously coagulating on titanium niobate nano-sheet.Desirably, the first one of the present invention is (2) the solid acidcatalyst of (1), wherein a Ti/Nb atomic ratio z is 1.2<z<1.4, moredesirably the first one of the present invention is (3) the solid acidcatalyst of (1) or (2), wherein organic amine or organic ammonium is atleast one selected from the group consisting of ethylamine, propylamineor tetrabutylammonium. Further desirably, the first one of the presentinvention is (4) the solid acid catalyst of (1), (2) or (3), wherein thesurface area of coagulated titanium niobate nano-sheet is 10 times ormore to the surface area of cation changeable lamellar metal oxideproton exchanger and is in the range from 60 m²g⁻¹ to 150 m²g⁻¹.

The second one of the present invention is an ester dehydrationcondensation catalyst composed of the solid acid catalyst of (1) to (4).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the drawing showing the synthesis process of the solid acidcatalysts represented by numerical marks from 1 to 5. In FIG. 1, 1 isthe protonation process which exchanges interlayer ions of lamellarmetal oxide with proton in aqueous solution of inorganic acid or organicacid, 2 is a process to prepare re-laminated anion nano-sheets 3 byinserting organic amine or organic ammonium cation between the layers ofsaid lamellar metal oxide proton exchanger and re-laminating and formingcolloid so as to prepare re-laminated anion nano-sheet (2 and 3 of FIG.1). 4 is a process showing to exchange absorbed organic cation withproton by adding inorganic acid or organic acid to said re-laminatedcolloidal solution and to re-coagulate on the nano-sheet composing solidacid catalyst 5.

FIG. 2 is the powder X ray diffraction spectrum of lamellar metal oxidefor synthesizing solid acid catalyst of Examples 1 and 2 and ComparativeExamples 1 and 2 (from the bottom, Comparative Example 1 (1C), Example 1(1), Example 2 (2) and Comparative Example 2 (2C) ) and synthesizedsolid acid catalysts therefrom.

FIG. 3 indicates the relationship between catalyst activity and Tinumber in catalyst composition when solid acid catalysts synthesized inExamples 1 and 2 and Comparative Examples 1 and 2 is used as an esterdehydration condensation catalyst and reacted for 6 hours.

DESCRIPTION OF THE PREFERRED EMBOBYMENT

The present invention will be illustrated more in detail.

A. The lamellar metal oxide which synthesizes solid acid catalyst of thepresent invention can be synthesized by baking a precursor comprisingsalt of Ti or Nb ion or metal ion of alkali metal ion or polymer in airat 500° C.-1500° C.

B. Process for synthesis of solid acid catalyst is shown in FIG. 1. Saidprocess is composed of,

1. Process to exchange interlayer ions of lamellar metal oxide obtainedin said A with protons in inorganic or organic aqueous solution of0.0001M-1M (1. of FIG. 1),

2. Process to insert 10 times or less amount of organic amine or organicammonium cation to the amount of the lamellar metal oxide protonexchanger (2 and 3 of FIG. 1) and forming colloidal solution byre-laminating from cation exchangeable lamellar metal oxide as a colloidto which said organic amine or organic ammonium cation is absorbed (2and 3 of FIG. 1) and

3. Process to exchange absorbed organic cations with protons by addinginorganic or organic aqueous solution of 0.0001M-1M to said re-laminatedcolloidal solution and to coagulate on a titanium niobate nano-sheet (4of FIG. 4).

Said each process can be progressed in room temperature.

C. As an acid to be used in the protonation process which synthesizesthe solid acid catalyst, both inorganic or organic acid can be used.

D. As an organic amine to be used in synthesizing process of the solidacid catalyst, alkyl amines such as ethyl amine, propyl amine or butylmine can be used. And as an organic ammonium, quaternary alkylammoniumcation such as tetrabutylammonium cation or tetraethylammonium cationcan be used.

EXAMPLE

The present invention will be illustrated more specifically according tothe Examples, however, not intending to limit the scope of the presentinvention.

Measuring Apparatus;

A. Powder X-ray diffraction spectrum of lamellar metal oxide andsynthesized solid acid catalyst are measured by Powder X-rayDiffractometory of Rigaku Co., Ltd.

B. Surface area of synthesized solid acid catalyst is measured by aSurface Area Measuring apparatus of COULTER Co., Ltd.

Example 1

Powder mixture of K₂CO₃, TiO₂, Nb₂O₅ is prepared by substance ratio1.1:1.1:0.9, and lamellar metal oxide K_(1.1)Ti_(1.1)Nb_(0.9)O₅ isobtained by calcination of the mixture in air at 800° C. for 12 hours.The powder X-ray diffraction spectrum of K_(1.1)Ti_(1.1)Nb_(0.9)O₅ isshown in FIG. 2. The surface area of K_(1.1)Ti_(1.1)Nb_(0.9)O₅ powder is1 m²g⁻¹. Powder of lamellar metal oxide proton exchanger ofH_(1.1)Ti_(1.1)Nb_(0.9)O₅ is obtained by dispersing 2 g ofK_(1.1)Ti_(1.1)Nb_(0.9)O₅ powder in 200 mL of 1M nitric acid andpenetrated for 14 hours then filtrated. 2 g of H_(1.1)Ti_(1.1)Nb_(0.9)O₅powder is dispersed in 150 mL of distilled water and add 15% aqueoussolution of tetrabutylammonium hydroxide and bring the pH of the aqueoussolution to 8-11 and stirred. During the stirring, pH of aqueoussolution is maintained 8-11 by adding 15 wt % of aqueous solution oftetrabutylammonium hydroxide. After stirring of 24 hours, whitedispersion is obtained. The obtained dispersion is centrifuged for 10minutes by 3000 rpm and the colloidal solution of Ti_(1.1)Nb_(0.9)O₅sheet to which tetrabutylammonium cation is absorbed is separated as asupernatant. When 20 mL of 0.1M nitric acid aqueous solution is added to30 mL of colloidal solution of Ti_(1.1)Nb_(0.9)O₅ sheet, the colloid ofTi_(1.1)Nb_(0.9)O₅ sheet is precipitated and the coagulation ofH_(1.1)Ti_(1.1)Nb_(0.9)O₅ sheet is obtained. The surface area ofH_(1.1)Ti_(1.1)Nb_(0.9)O₅ sheet coagulation is 153 m²g⁻¹.

Said H1.1Ti_(1.1)Nb_(0.9)O₅ sheet coagulation is vacuumed for 1 hour at150° C., poured into mixed solution of 0.1 mol of acetic acid and 0.1mol of ethyl alcohol under argon gas atmosphere, stirred for 6 hours at70° C., and amount of generation of ethyl acetate formed by acidcatalyst reaction is measured by a gas chromatography. Amount of ethylacetate formed by 6 hours reaction is shown in FIG. 3. It is understoodthat the generating speed of ethyl acetate in H_(1.1)Ti_(1.1)Nb_(0.9)O₅sheet coagulation is approximately 1.1 times larger than that ofH_(1.0)Ti_(1.0)Nb₁₀O₅.

Example 2

Powder mixture of K₂CO₃, TiO₂, Nb₂O₅ is prepared by substance ratio1.15:1.15:0.85, and lamellar metal oxide K_(1.15)Ti_(1.15)Nb_(0.85)O₅ isobtained by calcination of the mixture in air at 800° C. for 12 hours.The powder X-ray diffraction spectrum of K_(1.15)Ti_(1.15)Nb_(0.85)O₅ isshown in FIG. 2. The surface area of K_(1.15)Ti_(1.15)Nb_(0.85)O₅ powderis 1 m²g⁻¹. Powder of lamellar metal oxide proton exchanger ofH_(1.15)Ti_(1.15)Nb_(0.85)O₅ is obtained by dispersing 2 g ofK_(1.15)Ti_(1.15)Nb_(0.85)O₅ powder in 200 mL of 1M nitric acid andpenetrated for 14 hours then filtrated. 2 g of H_(1.1)Ti_(1.1)Nb_(0.9)O₅powder is dispersed in 150 mL of distilled water and add 15 wt % aqueoussolution of tetrabutylammonium hydroxide and bring the pH of the aqueoussolution to 8-11 and stirred. During the stirring, pH of aqueoussolution is maintained 8-11 by adding 15 wt % of aqueous solution oftetrabutylammonium hydroxide. After stirring for 24 hours, whitedispersion is obtained. The obtained dispersion is centrifuged for 10minutes by 3000 rpm and the colloidal solution of Ti_(1.15)Nb_(0.85)O₅sheet to which tetrabutylammonium cation is absorbed is separated as asupernatant. When 20 mL of 0.1M nitric acid aqueous solution is added to30 mL of colloidal solution of Ti_(1.15)Nb_(0.85)O₅ sheet, the colloidof Ti_(1.15)Nb_(0.85)O₅ sheet is precipitated and the coagulation ofH_(1.15)Ti_(1.15)Nb_(0.85)O₅ sheet is obtained. The surface area ofH_(1.15)Ti_(1.15)Nb_(0.85)O₅ sheet coagulation is 143 m²g⁻¹.

Said H_(1.15)Ti_(1.15)Nb_(0.85)O₅ sheet coagulation is vacuumed for 1hour at 150° C., poured into mixed solution of 0.1 mol of acetic acidand 0.1 mol of ethyl alcohol under argon gas atmosphere, stirred for 6hours at 70° C., and amount of generation of ethyl acetate formed byacid catalyst reaction is measured by a gas chromatography. Amount ofethyl acetate formed by 6 hours reaction is shown in FIG. 3. It isunderstood that the generating speed of ethyl acetate inH_(1.15)Ti_(1.15)Nb_(0.85)O₅ sheet coagulation is approximately 1.3times larger than that of H_(1.0)Ti_(1.0)Nb₁₀O₅.

Example 3

Powder mixture of K₂CO₃, TiO₂, Nb₂O₅ is prepared by substance ratio1.2:1.2:0.8 is prepared, and lamellar metal oxideK_(1.15)Ti_(1.15)Nb_(0.85)O₅ is obtained by calcination of the mixturein air at 800° C. for 12 hours. The powder X-ray diffraction spectrum ofk_(1.15)Ti_(1.15)Nb_(0.85)O₅ is shown in FIG. 2. The surface area ofK_(1.2)Ti_(1.2)Nb_(0.8)O₅ powder is 1 m²g⁻¹. Powder of lamellar metaloxide proton exchanger of H_(1.15)Ti_(1.15)Nb_(0.85)O₅ is obtained bydispersing 2 g of K_(1.2)Ti_(1.2)Nb_(0.8)O₅ powder in 200 mL of 1Mnitric acid and penetrated for 14 hours then filtrated. 2 g ofH_(1.2)Ti_(1.2)Nb_(0.8)O₅ powder is dispersed in 150 mL of distilledwater and add 15 wt % aqueous solution of tetrabutylammonium hydroxideand bring the pH of the aqueous solution to 8-11 and stirred. During thestirring, pH of aqueous solution is maintained to 8-11 by adding 15 wt %of aqueous solution of tetrabutylammonium hydroxide. After stirring of24 hours, white dispersion is obtained. The obtained dispersion iscentrifuged for 10 minutes by 3000 rpm and the colloidal solution ofTi_(1.2)Nb_(0.8)O₅ sheet to which tetrabutylammonium cation is absorbedis separated as a supernatant. When 20 mL of 0.1M nitric acid aqueoussolution is added to 30 mL of colloidal solution of Ti_(1.2)Nb_(0.8)O₅sheet, the colloid of Ti_(1.2)Nb_(0.8)O₅ sheet is precipitated and thecoagulation of H_(1.2)Ti_(1.2)Nb_(0.8)O₅ sheet is obtained. The surfacearea of H_(1.2)Ti_(1.2)Nb_(0.8)O₅ sheet coagulation is 110 m²g⁻¹.

Said H_(1.2)Ti_(1.2)Nb_(0.8)O₅ sheet coagulation is vacuumed for 1 hourat 150° C., poured into mixed solution of 0.1 mol of acetic acid and 0.1mol of ethyl alcohol under argon gas atmosphere, stirred for 6 hours at70° C., and amount of generation of ethyl acetate formed by acidcatalyst reaction is measured by a gas chromatography. Amount of ethylacetate formed by 6 hours reaction is shown in FIG. 3.

Comparative Example 1

Powder mixture of K₂CO₃, TiO₂, Nb₂O₅ is prepared by substance ratio1.0:1.0:1.0, and lamellar metal oxide K_(1.0)Ti_(1.0)Nb_(1.0)O₅ isobtained by calcination of the mixture in air at 800° C. for 12 hours.The powder X-ray diffraction spectrum of K_(1.0)Ti_(1.0)Nb_(1.0)O₅ isshown in FIG. 2. The surface area of K_(1.0)Ti_(1.0)Nb_(1.0)O₅ powder is1 m²g⁻¹. Powder of lamellar metal oxide proton exchanger ofH_(1.0)Ti_(1.0)Nb_(1.0)O₅ is obtained by dispersing 2 g ofK_(1.0)Ti_(1.0)Nb_(1.0)O₅ powder in 200 mL of 1M nitric acid andpenetrated for 14 hours then filtrated. 2 g of H_(1.0)Ti_(1.0)Nb_(1.0)O₅powder is dispersed in 150 mL of distilled water and add 15 wt % aqueoussolution of tetrabutylammonium hydroxide and bring the pH of the aqueoussolution to 8-11 and stirred. During the stirring, pH of aqueoussolution is maintained 8-11 by adding 15 wt % of aqueous solution oftetrabutylammonium hydroxide. After stirring of 24 hours, whitedispersion is obtained. The obtained dispersion is centrifuged for 10minutes by 3000 rpm and the colloidal solution of Ti_(1.0)Nb_(1.0)O₅sheet to which tetrabutylammonium cation is absorbed is separated as asupernatant. When 20 mL of 0.1M nitric acid aqueous solution is added to30 mL of colloidal solution of Ti_(1.0)Nb_(1.0)O₅ sheet, the colloid ofTi_(1.0)Nb_(1.0)O₅ sheet is precipitated and the coagulation ofH_(1.0)Ti_(1.0)Nb_(1.0)O₅ sheet is obtained. The surface area ofH_(1.0)Ti_(1.0)Nb_(1.0)O₅ sheet coagulation is 143 m²g⁻¹.

Said H_(1.0)Ti_(1.0)Nb_(1.0)O₅ sheet coagulation is vacuumed for 1 hourat 150° C., poured into mixed solution of 0.1 mol of acetic acid and 0.1mol of ethyl alcohol under argon gas atmosphere, stirred for 6 hours at70° C., and amount of generation of ethyl acetate formed by acidcatalyst reaction is measured by a gas chromatography. Amount of ethylacetate formed by 6 hours reaction is shown in FIG. 3.

Comparative Example 2

Powder mixture of K₂CO₃, TiO₂, Nb₂O₅ is prepared by substance ratio1.25:1.25:0.75, and lamellar metal oxide K_(1.25)Ti_(1.25)Nb_(0.75)O₅ isobtained by calcining the mixture in air at 800° C. for 12 hours. Thepowder X-ray diffraction spectrum of k_(1.25)Ti_(1.25)Nb_(0.75)O₅ isshown in FIG. 2. The peak of impurity originated from K₃Ti₅NbO₅ at wholerange becomes large, while the peak of KTiNbO₅ is confirmed to becomesmall. The surface area of K_(1.25)Ti_(1.25)Nb_(0.75)O₅ powder is 1m²g⁻¹. Powder of lamellar metal oxide proton exchanger ofH_(1.25)Ti_(1.25)Nb_(0.75)O₅ is obtained by dispersing 2 g ofK_(1.25)Ti_(1.25)Nb_(0.75)O₅ powder in 200 mL of 1M nitric acid andpenetrated for 14 days then filtrated. 2 g ofH_(1.25)Ti_(1.25)Nb_(0.75)O₅ powder is dispersed in 150 mL of distilledwater and add 15 wt % aqueous solution of tetrabutylammonium hydroxideand bring the pH of the aqueous solution to 8-11 and stirred. During thestirring, pH of aqueous solution is maintained 8-11 by adding 15 wt % ofaqueous solution of tetrabutylammonium hydroxide. After stirring of 24hours, white dispersion is obtained. The obtained dispersion iscentrifuged for 10 minutes by 3000 rpm and the colloidal solution ofTi_(1.25)Nb_(0.75)O₅ sheet to which tetrabutylammonium cation isabsorbed is separated as a supernatant. When 20 mL of 0.1M nitric acidaqueous solution is added to 30 mL of colloidal solution ofTi_(1.25)Nb_(0.75)O₅ sheet, the colloid of Ti_(1.25)Nb_(0.75)O₅ sheet isprecipitated and the coagulation of H_(1.25)Ti_(1.25)Nb_(0.75)O₅ sheetis obtained. The surface area of H_(1.25)Ti_(1.25)Nb_(0.75)O₅ sheetcoagulation is 110 m²g⁻¹.

Said H_(1.25)Ti_(1.25)Nb_(0.75)O₅ sheet coagulation is vacuumed for 1hour at 150° C., poured into mixed solution of 0.1 mol of acetic acidand 0.1 mol of ethyl alcohol under argon gas atmosphere, stirred for 6hours at 70° C., and amount of generation of ethyl acetate formed byacid catalyst reaction is measured by a gas chromatography. Amount ofethyl acetate formed by 6 hours reaction is shown in FIG. 2. It isconfirmed that the generating speed of ethyl acetate inH_(1.25)Ti_(1.25)Nb_(0.75)O₅ sheet coagulation is slower than that ofH_(1.0)Ti_(1.0)Nb₁₀O₅. It is obvious that the impurity phase K₃Ti₈O₁₇which is formed in the starting material deteriorates the acid catalystability.

INDUSTRIAL APPLICABILITY

As mentioned above, the present invention provides the excellent effectthat a solid acid catalyst which is usable for the catalyst ofdehydration reaction by controlling Ti/Nb atom ratio z and number of Ticontained in titanium niobate nano-sheet coagulation. Further, these areusable as the base material with possibilities, from the view point thatthe multi functionality of catalyst can be easily designed byembellishing polyanion nano-sheet with different kinds of metal ion orcationic complex.

1. A solid acid catalyst represented by HTi_(x)Nb_(y)O₅, wherein x is1.1<x<1.2 and y is 0.9>y>0.8, having a Ti/Nb atomic ratio z of 1<z<1.5,obtained by proton changing of alkali metal cation of cation changeablelamellar metal oxide in which polyanion nano-sheet comprising lamellarmetal oxide layers of titanium niobate lying alkali metal cation betweenare regularly laminated by inorganic acid or organic acid adjusted to0.0001M to 1M, delaminating said laminated layers temporarily byinserting cation selected from the group consisting of organic amine ororganic ammonium between layers of proton exchangers, preparing anaqueous colloidal solution comprising metal oxide sheets to which saidorganic amine or organic ammonium is absorbed, then proton exchangingsaid organic amine or organic ammonium by adding inorganic acid ororganic acid adjusted to 0.0001M to 1M to said aqueous colloidalsolution and simultaneously coagulating on titanium niobate nano-sheet.2. The solid acid catalyst of claim 1, wherein a Ti/Nb atomic ratio z is1.2<z<1.4.
 3. The solid acid catalyst of claim 1, wherein organic amineor organic ammonium is at least one selected from the group consistingof ethylamine, propylamine or tetrabutylammonium.
 4. The solid acidcatalyst of claim 1, wherein a Ti/Nb atomic ratio z is 1.2<z<1.4 andorganic amine or organic ammonium is at least one selected from thegroup consisting of ethylamine, propylamine or tetrabutylammonium. 5.The solid acid catalyst of claim 1, wherein the surface area ofcoagulated titanium niobate nano-sheet is 10 times or more to thesurface area of cation changeable lamellar metal oxide proton exchangerand is in the range from 60 m²g⁻¹ to 150 m²g⁻¹.
 6. The solid acidcatalyst of claim 1, wherein a Ti/Nb atomic ratio z is 1.2<z<1.4 and thesurface area of coagulated titanium niobate nano-sheet is 10 times ormore to the surface area of cation changeable lamellar metal oxideproton exchanger and is in the range from 60 m²g⁻¹ to 150 m²g⁻¹.
 7. Thesolid acid catalyst of claim 1, wherein a Ti/Nb atomic ratio z is1.2<z<1.4, organic amine or organic ammonium is at least one selectedfrom the group consisting of ethylamine, propylamine ortetrabutylammonium and the surface area of coagulated titanium niobatenano-sheet is 10 times or more to the surface area of cation changeablelamellar metal oxide proton exchanger and is in the range from 60 m²g⁻¹to 150 m²g⁻¹.
 8. An ester dehydration condensation catalyst comprisingthe solid acid catalyst of claim
 1. 9. An ester dehydration condensationcatalyst comprising the solid acid catalyst of claim
 2. 10. An esterdehydration condensation catalyst comprising the solid acid catalyst ofclaim
 3. 11. An ester dehydration condensation catalyst comprising thesolid acid catalyst of claim
 4. 12. An ester dehydration condensationcatalyst comprising the solid acid catalyst of claim
 5. 13. An esterdehydration condensation catalyst comprising the solid acid catalyst ofclaim
 6. 14. An ester dehydration condensation catalyst comprising thesolid acid catalyst of claim 7.